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Full text of "The manufacture and properties of iron and steel"

THE .ACID OPEN-HEARTH PROCESS.
181
from the scouring of the hearth are usually sufficient for the requirements of the cinder, hut with low-silicon pig-iron, free from adhering sand, it may be necessary to add additional silica to prevent the basic slag from making inroads upon the bottom. On the contrary, if the silicon in the pig-iron is- high, the slag will he
TABLE X-A. Elimination of Metalloids in an Open-Hearth Charge.
Nature of Sample.	Group I.	Group II.
	11,700	20,700
	45,550	86,800
		
-                                 (Si Composition of original charge, per cent, (estimated) < Mn (C	0.40 0.90 1.00	0.65 0.85 1.50
(Si	.02 .09	.05 .08
	.54	.64
(SiO,	50.24 21.67	49.46 18.16
/ FeO	23.91 •	88.27
viscous and infusible. Manganese helps to counteract this viscosity, but in the absence of this element iron oxide must be added in the shape of ore, or formed from the bath by waste of iron.
The way in which the me.talloids are eliminated during the-melting will be understood from Table X-A. Each column represents the average of consecutive charges; Group I includes nineteen heats melted with soft-coal producer gas, and Group II six heats made with oil vapor. The.oil vapor is more oxidizing than the coal gas, so> that although the original charge was higher in oxygen-absorbing elements, the bath, after melting, had the same composition in both' cases. The slag shows a great variation in. the oxides of iron and manganese, for the amount of manganese was limited by the content in the charge, and since the slag required a certain proportion of bases, the deficit was made up by oxidation of iron.
SEC. Xc.—Chemical history after melting.—After the melting! it is necessary to oxidize the remaining carbon, manganese, and silicon, by keeping the bath at a high heat and adding iron ore in successive doses, thus forming silica and oxide of manganese,which go into the slag, and carbonic1 oxide which escapes with the flame. This combustion of carbon produces a bubbling over the entire surface of the bath, exposing the metal to the flame, and keeping it at